scholarly journals Numerical Analysis of Blood Flow Through Discrete Stenosis: Role of Eccentricity and Spacing Ratio

2017 ◽  
Author(s):  
Siyeong Ju ◽  
Linxia Gu
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Recirculation Zone ◽  
Cfd Simulation ◽  
Flow Region ◽  
Flow Recirculation ◽  
Spacing Ratio ◽  
Computational Fluid Dynamics Cfd ◽  
Flow Interference

Stenosis or narrowing of arteries induces a turbulent flow region downstream. Multiple stenosis may lead to flow interference and further disturb the blood flow. This has important clinical implications [1], such as disturbed blood flow and flow recirculation which were correlated with the development of atherosclerosis by upregulating the endothelial cells genes and proteins that cause atherogenesis [2]. Numerical simulation of concentric stenoses by Lee et al [3] have shown that the recirculation zone following the first concentric stenosis affected the flow field at the downstream of the second one, which was dependent on the spacing ratio and degree of stenosis. However, the majority of stenosis is eccentric [2] and the detailed fluid dynamics of multiple stenoses with eccentric constrictions is lacking. The aim of this study is to investigate the interactions between double stenoses with eccentricity using computational fluid dynamics (CFD) simulation. The role of spacing ratio on the recirculation zone and turbulence intensity (TI) were characterized and also compared to concentric cases.

scholarly journals A Workflow for Patient-Individualized Virtual Angiogram Generation Based on CFD Simulation

2012 ◽  
Vol 2012 ◽  
pp. 1-24 ◽  
Author(s):  
Jürgen Endres ◽  
Markus Kowarschik ◽  
Thomas Redel ◽  
Puneet Sharma ◽  
Viorel Mihalef ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Blood Flow ◽  
Shear Stress ◽  
Cfd Simulation ◽  
Cerebral Aneurysms ◽  
Patient Specific ◽  
Hemodynamic Parameters ◽  
Risk Of Rupture ◽  
Computational Fluid Dynamics Cfd ◽  
Subsequent Comparison

Increasing interest is drawn on hemodynamic parameters for classifying the risk of rupture as well as treatment planning of cerebral aneurysms. A proposed method to obtain quantities such as wall shear stress, pressure, and blood flow velocity is to numerically simulate the blood flow using computational fluid dynamics (CFD) methods. For the validation of those calculated quantities, virtually generated angiograms, based on the CFD results, are increasingly used for a subsequent comparison with real, acquired angiograms. For the generation of virtual angiograms, several patient-specific parameters have to be incorporated to obtain virtual angiograms which match the acquired angiograms as best as possible. For this purpose, a workflow is presented and demonstrated involving multiple phantom and patient cases.

Effect of Baffle Openings to the Flow Distribution in a SERVCO Fume Cupboard

2014 ◽  
Vol 660 ◽  
pp. 719-723
Author(s):  
Mohd Amal Asrol Omar ◽  
Wirachman Wisnoe ◽  
Azman Bakri
Keyword(s):  
Fluid Dynamics ◽  
Cross Sections ◽  
Recirculation Zone ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Recirculation Region ◽  
Large Size ◽  
Airflow Distribution ◽  
Potential Contributor ◽  
Computational Fluid Dynamics Cfd

Recirculation region behind a fume cupboard sash is the potential contributor to the leakage of the contaminants due to its large size. This is found from the computational fluid dynamics (CFD) simulation of SERVCO fume cupboard using κ-ω turbulence model. For a good fume cupboard, the recirculation zone needs to be minimized while maintaining the flow distribution to all area in the fume cupboard. The opening on the baffle may reduce the recirculation zone which in turn may reduce back flow that is the cause of leakage. In this paper, the effect of shape of baffle openings on flow distributions of a SERVCO fume cupboard will be presented as a result of CFD. The results are presented in terms of velocity vectors Vy (in the direction towards the sash opening) at different cross sections for 4 opening shapes. The opening is found to improve the airflow distribution.

Effect of Baffle Opening Position to the Flow Distribution in a Servco Fume Cupboard

2013 ◽  
Vol 465-466 ◽  
pp. 566-570 ◽  
Author(s):  
Mohd Amal Asrol Omar ◽  
Wirachman Wisnoe ◽  
Azman Bakri
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Turbulence Model ◽  
Cross Sections ◽  
Recirculation Zone ◽  
Cfd Simulation ◽  
Flow Distribution ◽  
Recirculation Region ◽  
Potential Contributor ◽  
Computational Fluid Dynamics Cfd

From the computational fluid dynamics (CFD) simulation of Servco fume cupboard using κ-ω turbulence model, it is found that recirculation region behind the sash is the potential contributor to the leakage of the contaminants due to its large size. To have a good fume cupboard, the recirculation zone needs to be minimised while maintaining the flow distributions to all area in the fume cupboard. The opening on the baffle may reduce the recirculation zone which in turn may reduce back flow that can be the cause of leakage. In this paper, the effect of baffle openings on flow distributions of a Servco fume cupboard will be presented as a result of computational fluid dynamics (CFD) simulation using κ-ω turbulence model. The results are presented in terms of magnitude of curl of velocity vectors Vxyzat different cross sections of the fume cupboard for 4 variations of location of baffles opening.

scholarly journals Computational Fluid Dynamics (CFD) Simulation on Mixing in T-Shaped Micromixer

2020 ◽  
Vol 932 ◽  
pp. 012006
Author(s):  
S N A Ahmad Termizi ◽  
C Y Khor ◽  
M A M Nawi ◽  
Nurlela Ahmad ◽  
Muhammad Ikman Ishak ◽  
...  
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Cfd Simulation ◽  
Computational Fluid Dynamics Cfd

A Study on the Performance of Stratified Air Conditioning Design in Assembly Halls – A Case Study at the Dazhi Cultural Center in Taiwan

2013 ◽  
Vol 368-370 ◽  
pp. 599-602 ◽  
Author(s):  
Ian Hung ◽  
Hsien Te Lin ◽  
Yu Chung Wang
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Indoor Air ◽  
Air Conditioning ◽  
Cfd Simulation ◽  
Indoor Temperature ◽  
Cultural Center ◽  
Computational Fluid Dynamics Cfd

This study focuses on the performance of air conditioning design at the Dazhi Cultural Center and uses a computational fluid dynamics (CFD) simulation to discuss the differences in wind velocity and ambient indoor temperature between all-zone air conditioning design and stratified air conditioning design. The results have strong implications for air conditioning design and can improve the indoor air quality of assembly halls.

Design Approach for the Development of the Flow Field of Bipolar Plates for a PEMFC Stack Prototype

2014 ◽  
Vol 11 (6) ◽  
Author(s):  
Paolo Sala ◽  
Paola Gallo Stampino ◽  
Giovanni Dotelli
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Fuel Cell ◽  
Cfd Simulation ◽  
Bipolar Plates ◽  
Flow Rates ◽  
Gas Leakage ◽  
Auxiliary Power ◽  
Computational Fluid Dynamics Cfd ◽  
Enhance Mass

This work is part of a project whose final aim is the realization of an auxiliary power fuel cell generator. It was necessary to design and develop bipolar plates that would be suitable for this application. Bipolar plates have a relevant influence on the final performances of the entire device. A gas leakage or a bad management of the water produced during the reaction could be determinant during operations and would cause the failure of the stack. The development of the bipolar plates was performed in different steps. First, the necessity to make an esteem of the dynamics that happen inside the feeding channels led to perform analytical calculations. The values found were cross-checked performing a computational fluid dynamics (CFD) simulation; finally, it was defined the best pattern for the feeding channels, so that to enhance mass transport and achieve the best velocity profile. The bipolar plates designed were machined and assembled in a laboratory scale two cells prototype stack. Influences of the temperature and of the humidity were evaluated performing experiments at 60 deg and 70 deg and between 60% and 100% of humidity of the reactant gasses. The best operating point achieved in one of these conditions was improved by modifying the flow rates of the reactant, in order to obtain the highest output power, and it evaluated the reliability of the plates in experiments performed for longer times, at fixed voltages.

Computational Fluid Dynamics (CFD) Study of the 4th Generation Prototype of a Continuous Flow Ventricular Assist Device (VAD)

2004 ◽  
Vol 126 (2) ◽  
pp. 180-187 ◽  
Author(s):  
Xinwei Song ◽  
Houston G. Wood ◽  
Don Olsen
Keyword(s):  
Fluid Dynamics ◽  
Computational Fluid Dynamics ◽  
Blood Flow ◽  
Ventricular Assist Device ◽  
Continuous Flow ◽  
Surrounding Tissue ◽  
Assist Device ◽  
Ventricular Assist ◽  
Wide Range ◽  
Computational Fluid Dynamics Cfd

The continuous flow ventricular assist device (VAD) is a miniature centrifugal pump, fully suspended by magnetic bearings, which is being developed for implantation in humans. The CF4 model is the first actual prototype of the final design product. The overall performances of blood flow in CF4 have been simulated using computational fluid dynamics (CFD) software: CFX, which is commercially available from ANSYS Inc. The flow regions modeled in CF4 include the inlet elbow, the five-blade impeller, the clearance gap below the impeller, and the exit volute. According to different needs from patients, a wide range of flow rates and revolutions per minute (RPM) have been studied. The flow rate-pressure curves are given. The streamlines in the flow field are drawn to detect stagnation points and vortices that could lead to thrombosis. The stress is calculated in the fluid field to estimate potential hemolysis. The stress is elevated to the decreased size of the blood flow paths through the smaller pump, but is still within the safe range. The thermal study on the pump, the blood and the surrounding tissue shows the temperature rise due to magnetoelectric heat sources and thermal dissipation is insignificant. CFD simulation proved valuable to demonstrate and to improve the performance of fluid flow in the design of a small size pump.

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